Wenling Zhang

Self-assembly preparation of SiO2@Ni-Al layered double hydroxide composites and their enhanced electrorheological characteristics

The core-shell structured SiO2@Ni-Al layered double hydroxide (LDH) composites were prepared via self-assembly of Ni-Al LDH on the surface of SiO2 spheres. Only coating a layer of ultrathin Ni-Al LDH sheet, the resulting SiO2@Ni-Al LDH composites exhibit significantly enhanced electrorheological (ER) characteristics compared to conventional bare SiO2 spheres. The monodispersed SiO2 spheres with average diameters of 260 nm were synthesized by the hydrolysis of tetraethyl orthosilicate (TEOS), while the shell part, Ni-Al LDH sheet was prepared by the hydrothermal procedure. The morphology of the samples was investigated via scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structure of the samples was characterized by X-ray diffraction (XRD). The species and distribution of elements in samples were confirmed by X-ray photoelectron spectroscopy (XPS), Energy dispersive analysis of X-ray (EDX) and elemental mapping in STEM. Subsequently, the ER characteristics of the composites dispersed in insulating oil were characterized by a rotational rheometer. The electric field-stimulated rheological performances (yield stress, viscosity, modulus, etc.) were observed under an external electric field, which is different from the Newtonian state in the free electric field.

2D MoS2/graphene composites with excellent full Ku band microwave absorption

Increasing attention has been focused on microwave absorption (MA) performance in the Ku band (12.4–18.0 GHz) due to the rapid development of radar, military aircraft and satellite communications. In this work, 2D heterostructure MoS2/graphene composites were proven to be promising full Ku band MA materials due to their superb characteristics of high dielectric loss, low density, large surface area and good thermal stability. By a simple one step solvothermal method, MoS2/graphene composites were successfully obtained, and the matched 2D structure between MoS2 and graphene could generate synergistic effects and maximize the MA properties. Only with 30 wt% of the as-prepared MoS2/graphene composites, excellent MA properties in wide frequency bands were obtained. An optimal reflection loss (RL) value of −41.9 dB was obtained at 16.1 GHz with a thickness of 2.4 mm and the RL values exceeding −10 dB were achieved in the whole Ku band (12.2–18.0 GHz) with a thickness of 2.6–3.0 mm.

Towards unique shear thinning behaviors under electric and magnetic fields achieved by TiO2 decorated magnetic MoS2 nanosheets: lubricating effects

Discovering the relationship of structure and rheological behaviors remains challenging. In this study, the TiO2 nanoparticle decorated magnetic MoS2 nanosheets (Fe3O4@MoS2@TiO2 nanoparticles) exhibited unique rheological behaviors under external electric and magnetic fields owing to their special hierarchical structures. The constructed core–shell structures of the Fe3O4@MoS2@TiO2 nanoparticles were confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The magnetic behaviors were studied using a vibrating sample magnetometer (VSM). The Fe3O4@MoS2@TiO2 nanoparticles exhibited both electrorheological (ER) and magnetorheological (MR) properties that result from the decoration of high dielectric TiO2 nanoparticles on the MoS2 shell and paramagnetic behavior of Fe3O4 nanoparticles in the core, respectively. The MoS2 nanosheets act as superb lubricant at a high shear rate due to their weak interlayer van der Waals forces. The abrupt decrease of shear stress at a critical shear rate was observed under the external magnetic field and the proposed mechanism was also discussed. The unique rheological behaviors of the Fe3O4@MoS2@TiO2 nanoparticle based suspensions highlight the great promise of MoS2-based materials for cornerstone applications in rheological fields.